API for Garbage Collection

We are using WLS 6.1 SP3 on a Solaris machine. Is there any API we can use to
automate garbage collection instead of manually doing through the Admin Console.
Thanks in advance.

I can't answer or help with all of those… Here are my thoughts… The dollar object properties and functions can be called on by script from AI, BR, ID & PS… They are NOT restricted for use in the ESTK tookit. Yeah $.writeln() would write to the console if the toolkit were open if NOT then it will probably launch it… So remove or comment these out. As you can see from $.sleep() it does what it says when run in the host app. #targetengine is exclusive to ID this app can have multi-instances ( or something like that ). The other apps have 1 engine and thats it. AI's engine is persistent so wrapping your code is good practice I do this for BR & PS too… See…
http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/pdf/illustrator/scrip ting/readme_cs5.txt
As for garbage collection I've never fould the need to use it… I see some like to set variables back to null but again I don't do this…
You would have been better off asking this question in the ID scripting forum… There are several people there who are better qualified to answer some of this…

Similar Messages

High cpu usage for garbage collection (uptime vs total gc time)

Hi Team,
We have a very high cpu usage issue in the production.
When we restart the server, the cpu idle time would be around 95% and it comes down as days goes by. Today idle cpu is 30% and it is just 6th day after the server restart.
Environemnt details:
Jrockit version:
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_05-b04)
BEA WebLogic JRockit(TM) 1.4.2_05 JVM R24.4.0-1 (build ari-38120-20041118-1131-linux-ia32, Native Threads, GC strategy: parallel)
Gc Algorithm: JRockit Garbage Collection System currently running strategy: Single generational, parallel mark, parallel sweep
Number Of Processors: 4
Max Heap Size: 1073741824
Total Garbage Collection Time: 21:43:56.5
Uptime: 114:33:4.1
Total Garbage Collection Count: 420872
Total Number Of Threads: 198
Number Of Daemon Threads: 191
Can you guys please tell me what would be problem in the server which causing the high cpu usage?
One more thing I would like to know is that why the total number of threads is 198 when we specified the Executor pool size as 25? I agree that weblogic would create some threads for its maintenance but around 160 threads!!! something is wrong I guess.
Santhosh.
[email protected]

Hi,
I'm having a similar problem, but haven't been able to resolve it yet. Troubleshooting is made even harder by the fact that this is only happening on our production server, and I've been unable to reproduce it in the lab.
I'll post whatever findings I have and hopefully we'll be able to find a solution with the help of BEA engineers.
In my case, I have a stand-alone Tomcat server that runs fine for about 1-2 days, and then the JVM suddenly starts using more CPU, and as a result, the server load shoots up (normal CPU utilization is ~5% but eventually goes up to ~95%; load goes from 0.1 to 4+).
What I have found so far is that this corresponds to increased GC activity.
Let me list my environment specs before I proceed, though:
CPU: Dual Xeon 3.06GHz
RAM: 2GB
OS: RHEL4.4 (2.6.9-42.0.2.ELsmp)
JVM build 1.5.0_03-b07 (BEA JRockit(R) (build dra-45238-20050523-2008-linux-ia32, R25.2.0-28))
Tomcat version 5.5.12
JAVA_OPTS="-Xms768m -Xmx768m -XXtlasize16k -XXlargeobjectlimit16k -Xverbose:memory,cpuinfo -Xverboselog:/var/log/tomcat5/jvm.log -Xverbosetimestamp"
Here are excerpts from my verbose log (I'm getting some HT warning, not sure if that's a problem):
[Fri Oct 20 15:54:18 2006][22855][cpuinfo] Detected SMP with 2 CPUs that support HT.
[Fri Oct 20 15:54:18 2006][22855][cpuinfo] Trying to determine if HT is enabled.
[Fri Oct 20 15:54:18 2006][22855][cpuinfo] Trying to read from /dev/cpu/0/cpuid
[Fri Oct 20 15:54:18 2006][22855][cpuinfo] Warning: Failed to read from /dev/cpu/0/cpuid
[Fri Oct 20 15:54:18 2006][22855][cpuinfo] Trying to read from /dev/cpu/1/cpuid
[Fri Oct 20 15:54:18 2006][22855][cpuinfo] Warning: Failed to read from /dev/cpu/1/cpuid
[Fri Oct 20 15:54:18 2006][22855][cpuinfo] HT is: supported by the CPU, not enabled by the OS, enabled in JRockit.
[Fri Oct 20 15:54:18 2006][22855][cpuinfo] Warning: HT enabled even though OS does not seem to support it.
[Fri Oct 20 15:54:55 2006][22855][memory ] GC strategy: System optimized over throughput (initial strategy singleparpar)
[Fri Oct 20 15:54:55 2006][22855][memory ] heap size: 786432K, maximal heap size: 786432K
[Fri Oct 20 16:07:30 2006][22855][memory ] Changing GC strategy to generational, parallel mark and parallel sweep
[Fri Oct 20 16:07:30 2006][22855][memory ] 791.642-791.874: GC 786432K->266892K (786432K), 232.000 ms
[Fri Oct 20 16:08:02 2006][22855][memory ] 824.122: nursery GC 291998K->274164K (786432K), 175.873 ms
[Fri Oct 20 16:09:51 2006][22855][memory ] 932.526: nursery GC 299321K->281775K (786432K), 110.879 ms
[Fri Oct 20 16:10:24 2006][22855][memory ] 965.844: nursery GC 308151K->292222K (786432K), 174.609 ms
[Fri Oct 20 16:11:54 2006][22855][memory ] 1056.368: nursery GC 314718K->300068K (786432K), 66.032 ms
[Sat Oct 21 23:21:09 2006][22855][memory ] 113210.427: nursery GC 734274K->676137K (786432K), 188.985 ms
[Sat Oct 21 23:30:41 2006][22855][memory ] 113783.140: nursery GC 766601K->708592K (786432K), 96.007 ms
[Sat Oct 21 23:36:15 2006][22855][memory ] 114116.332-114116.576: GC 756832K->86835K (786432K), 243.333 ms
[Sat Oct 21 23:48:20 2006][22855][memory ] 114841.653: nursery GC 182299K->122396K (786432K), 175.252 ms
[Sat Oct 21 23:48:52 2006][22855][memory ] 114873.851: nursery GC 195060K->130483K (786432K), 142.122 ms
[Sun Oct 22 00:01:31 2006][22855][memory ] 115632.706: nursery GC 224096K->166618K (786432K), 327.264 ms
[Sun Oct 22 00:16:37 2006][22855][memory ] 116539.368: nursery GC 246564K->186328K (786432K), 173.888 ms
[Sun Oct 22 00:26:21 2006][22855][memory ] 117122.577: nursery GC 279056K->221543K (786432K), 170.367 ms
[Sun Oct 22 00:26:21 2006][22855][memory ] 117123.041: nursery GC 290439K->225833K (786432K), 69.170 ms
[Sun Oct 22 00:29:10 2006][22855][memory ] 117291.795: nursery GC 298947K->238083K (786432K), 207.200 ms
[Sun Oct 22 00:39:05 2006][22855][memory ] 117886.478: nursery GC 326956K->263441K (786432K), 87.009 ms
[Sun Oct 22 00:55:22 2006][22855][memory ] 118863.947: nursery GC 357229K->298971K (786432K), 246.643 ms
[Sun Oct 22 01:08:17 2006][22855][memory ] 119638.750: nursery GC 381744K->322332K (786432K), 147.996 ms
[Sun Oct 22 01:11:22 2006][22855][memory ] 119824.249: nursery GC 398678K->336478K (786432K), 93.046 ms
[Sun Oct 22 01:21:35 2006][22855][memory ] 120436.740: nursery GC 409150K->345186K (786432K), 81.304 ms
[Sun Oct 22 01:21:38 2006][22855][memory ] 120439.582: nursery GC 409986K->345832K (786432K), 153.534 ms
[Sun Oct 22 01:21:42 2006][22855][memory ] 120443.544: nursery GC 410632K->346473K (786432K), 121.371 ms
[Sun Oct 22 01:21:44 2006][22855][memory ] 120445.508: nursery GC 411273K->347591K (786432K), 60.688 ms
[Sun Oct 22 01:21:44 2006][22855][memory ] 120445.623: nursery GC 412391K->347785K (786432K), 68.935 ms
[Sun Oct 22 01:21:45 2006][22855][memory ] 120446.576: nursery GC 412585K->348897K (786432K), 152.333 ms
[Sun Oct 22 01:21:45 2006][22855][memory ] 120446.783: nursery GC 413697K->349080K (786432K), 70.456 ms
[Sun Oct 22 01:34:16 2006][22855][memory ] 121197.612: nursery GC 437378K->383392K (786432K), 165.771 ms
[Sun Oct 22 01:37:37 2006][22855][memory ] 121398.496: nursery GC 469709K->409076K (786432K), 78.257 ms
[Sun Oct 22 01:37:37 2006][22855][memory ] 121398.730: nursery GC 502490K->437713K (786432K), 65.747 ms
[Sun Oct 22 01:44:03 2006][22855][memory ] 121785.259: nursery GC 536605K->478156K (786432K), 132.293 ms
[Sun Oct 22 01:44:04 2006][22855][memory ] 121785.603: nursery GC 568408K->503635K (786432K), 71.751 ms
[Sun Oct 22 01:50:39 2006][22855][memory ] 122180.985: nursery GC 591332K->530811K (786432K), 131.831 ms
[Sun Oct 22 02:13:52 2006][22855][memory ] 123573.719: nursery GC 655566K->595257K (786432K), 117.311 ms
[Sun Oct 22 02:36:04 2006][22855][memory ] 124905.507: nursery GC 688896K->632129K (786432K), 346.990 ms
[Sun Oct 22 02:50:24 2006][22855][memory ] 125765.715-125765.904: GC 786032K->143954K (786432K), 189.000 ms
[Sun Oct 22 02:50:26 2006][22855][memory ] 125767.535-125767.761: GC 723232K->70948K (786432K), 225.000 ms
vvvvv
[Sun Oct 22 02:50:27 2006][22855][memory ] 125768.751-125768.817: GC 712032K->71390K (786432K), 64.919 ms
[Sun Oct 22 02:50:28 2006][22855][memory ] 125769.516-125769.698: GC 711632K->61175K (786432K), 182.000 ms
[Sun Oct 22 02:50:29 2006][22855][memory ] 125770.753-125770.880: GC 709632K->81558K (786432K), 126.000 ms
[Sun Oct 22 02:50:30 2006][22855][memory ] 125771.699-125771.878: GC 708432K->61368K (786432K), 179.000 ms
So, I'm running with the default GC strategy which lets the GC pick the most suitable approach (single space or generational). It seems to switch to generational almost immediately and runs well - most GC runs are in the nursery, and only once in a while it goes through the older space.
Now, if you look at [Sun Oct 22 02:50:27 2006], that's when everything changes. GC starts running every second (later on it's running 3 times a second) doing huge sweeps. It never goes through the nursery again, although the strategy is still generational.
It's all downhill from this point on, and it's a matter of hours (maybe a day) before we restart the server.
I guess my only question is: What would cause such GC behavior?
I would appreciate your ideas/comments!
Thanks,
Tenyo

Which algirithm is being used by java runtime for garbage collection??

On what basis does java reclaim objects using Garbage Collection ??
and explain the method i.e the step by step basis on how it is being done??

There are various whitepapers and the like on this.
As far as which objects may be collected, it's just any object that isn't referred to - directly or indirectly - by one of the root set of threads in the JVM.
Collecting algorithms vary from jvm to jvm. You'd do better to search the web for a whitepaper on the subject.
~Cheers

Elligible for Garbage Collection

If an object is unreferenced, but it does not declare a finalize() method, then is this object elligible to be finalized and freed by Gc?
Regards
JS

Thanks for the prompt reply.
JVM Specification says an object can be garbage collected when it is unreferenced.Thus that mean that setting an object to null can not make it elligible since some other objects may still refer the object in question?
JS

When will the demo object be eleigible for garbage collection?

class Test {
     private Demo d;
     void start() {
     d = new Demo();
     this.takeDemo(d);
     void takeDemo(Demo demo) {
     demo = null;
     demo = new Demo();
     }

Hey flounder, I am myself confused about garbage collection and assertions (yesterday)... Anyway because of ur interest in answering my query, I'll give one more try... But, if it's wrong, Please help me out.
The Demo (not demo) object created at line 4 has one 'this' reference on the next line. And as soon as this reference is eleigible, I guess even Demo d will be eligible. Correct?

Need for garbage collection using Webdynpro Binary Cache?

Dear Sirs,
I am using the Wiki guide, Exporting Table Data Using On-Demand Streams to export table data to Excel. (this is using Webdynpro binary cache)
Everything is working fine, however I would like to check prior to transport to production, if i need to do any garbage collection using this solution.
My biggest fear is if the all the excel files generated are stored forever, thus filling up the disk space or memory and crashing the production server.
Can anyone give me advice ?
best regards,
Jørgen Ruud

<b>Hi
Check This URL
Memory Usage
http://help.sap.com/saphelp_nw04/helpdata/en/98/f73c41325fa831e10000000a1550b0/frameset.htm
Resource Management
http://help.sap.com/saphelp_nw04/helpdata/en/15/d73f41d900db2be10000000a1550b0/frameset.htm
Regards
Chandran S</b>

Is this object available for garbage collection

public class MyClass {
public static void main(String args []){
new MyClass().myFunc();
//Because I don't assign this reference to a variable, is it available for collection at this point?
public void myFunc(){ }
Thanks ..... Jimmy

What do you mean "in most cases"? I assume you don't
mean that most methods in any java program should be
static, Of course not... please actually read the context of my post. "in most cases" where the code is similar to what the OP posted, a static method would probably be appropriate. In code where you are creating a new instance of a class for the sole purpose of calling a method and not retaining a reference to it, it should probably be a static method. Look at the OP's code:
public class MyClass {
public static void main(String args []){
new MyClass().myFunc();
public void myFunc(){
}Notice that the OP does not keep a reference to the object, simply calling a method and leaving it at that. I am saying that in this situation, it would probably be more appropriate to do the following:
public class MyClass {
public static void main(String args []){
MyClass().myFunc();
public static void myFunc(){
}I imagine that there are situations where the OP's original design may be useful, but in most situations, a static method is appropriate.
This isn't that complicated... I see no need to get into an argument over it. Please don't just attempt to make me look like a fool (I do a fine job of that on my own).

Calling of finalize() for garbage collection

Garbage collector will call the �finalize()� only once for an object. If any exception thrown while executing the finalize() that causes not to complete the execution of this method.
If this is the case, will the JVM assure that finalize() be called once again on this object.

Finalize is pretty obsolete. The danger is that a finalize method might export a reference to a defunct object, thus making it "reachable" again.
There's no guaranteed way of automatically doing special cleanup in Java, but if you want to do tidying up (e.g. releasing external resources) you should use a PhantomReference with a ReferenceQueue, and dedicate a thread to doing the cleanup.

Garbage Collection: how many objects are created after for loop?

Please see the fallowing java code
1 public class Test1 {
2
3     public static void main(String[] args) {
4
5          MyObj obj = null;
6          for(int i=0;i<5;i++){
7               obj = new MyObj();
8          }
9 // do something
10
11     }
12 }
so my question is How may objects are eligible for garbage collection at line no: 9 (// do something)?

so my question is How may objects are eligible for
garbage collection at line no: 9 (// do something)?It's impossible to answer that question since we don't know how MyObj is implemented.
Kaj

[JS] $.gc() - garbage collection, etc.

Hello everyone, bear with me for all the questions.
$.gc() - Initiates garbage collection in the JavaScript engine.
Ok, maybe I have a fundamental misunderstanding of things here, but I am wanting to understand a few things:
I was wanting to know if $.gc() can be called and executed outside of running scripts directly from with in the ESTK toolkit? The reason I ask is that its listed in the tools guide but not the javascript reference. I know things like $.writeln() only seem to apply/display from with in the ETSK toolkit, is it still executed otherwise silently when it appears in a script, $.sleep() works fine when used. So what about $.gc(), can I call it and have it execute from within my scripts outside of running them via the ETSK toolkit?
Is there a way to test if its in fact being called, executed, working? I have seen people talking about calling it twice and doubling up, $.gc() $.gc(), thus does it even work, or is it just a fabled mythical thing.
Do codes when executed outside the ETSK toolkit get funneled through the same javascript runtime engine that they do when executing from with in the ETSK toolkit? Is it all the same and the ETSK toolkit is just Adobe's GUI for writing, debugging, targeting different api's for the various programs with in the same underlying engine?
Does ScriptBay tap into and use this same underlying framework? Does it do anything inherently on its own for garbage collection? (since it can run scripts sequentially, repetitively, etc..)
Does anyone know what embedded javascript runtime/engine Adobe is using? This would be beneficial for any specific optimizations that can be considered or kept in mind in general based on the specific JS engine thats implemented when coding.
So aside from the mythical $.gc() , what other best practices for garbage collection should be considered? I know people suggest wrapping your codes in a function, talk of #targetengine (saw in InDesign forum), etc… are there any other common do's and dont's, best practices pertaining specifically to illustrator? Granted I can find a lot about Javascript in general across the web but what about how it applies to Illustrator, its api, limitations, performance, garbage collection, etc..
Thanks. ;-)
Again, sorry for all the questions, I am still trying to continue to wrap my head around different aspects of this whole thing. Thanks everyone for any feedback your able to offer and provide. Many thanks in advance, its greatly appreciated. Thanks again.

I can't answer or help with all of those… Here are my thoughts… The dollar object properties and functions can be called on by script from AI, BR, ID & PS… They are NOT restricted for use in the ESTK tookit. Yeah $.writeln() would write to the console if the toolkit were open if NOT then it will probably launch it… So remove or comment these out. As you can see from $.sleep() it does what it says when run in the host app. #targetengine is exclusive to ID this app can have multi-instances ( or something like that ). The other apps have 1 engine and thats it. AI's engine is persistent so wrapping your code is good practice I do this for BR & PS too… See…
http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/pdf/illustrator/scrip ting/readme_cs5.txt
As for garbage collection I've never fould the need to use it… I see some like to set variables back to null but again I don't do this…
You would have been better off asking this question in the ID scripting forum… There are several people there who are better qualified to answer some of this…

URL class is not being garbage collected

I have created two instances of the URL class to specify a file location for each image. I use com.symantec.itools.javax.swing.icons.ImageIcon class to display images specified by each URL instance as icons inside a button. The setImageLocation method(URL location) of the ImageIcon class sets the location to be displayed by this icon. The following is the code snippets used to create the ImageIcon instances:
private URL greenIconURL;
private URL redIconURL;
com.symantec.itools.javax.swing.icons.ImageIcon green_icon = new com.symantec.itools.javax.swing.icons.ImageIcon();
com.symantec.itools.javax.swing.icons.ImageIcon red_icon = new com.symantec.itools.javax.swing.icons.ImageIcon();
try
greenIconURL = new java.net.URL
("file:./images/greenline.gif");
green_icon.setImageLocation(greenIconURL);
catch (java.net.MalformedURLException error) { }
try
redIconURL = new java.net.URL
("file:./images/redline.gif");
red_icon.setImageLocation(redIconURL);
catch (java.net.MalformedURLException error) { }
I am using JProbe 5.0.1 Memory to determine the loitering objects when I remove the button from the JInternalFrame. I am using Java 1.2.2_08 version. The JProbe Memory Leak Doctor indicates that each URL instance has a reference to an entry in a HashMap table. The reference graph from the root set has a reference to SoftCache to HashMap to HashMap$Entry. To make this URL instance eligible for garbage collection, JProbe Memory Leak Doctor indicates I must remove the entry from the HashMap. How do I get access to this HashMap to remove the entry? If this is a problem with the version of the JDK, please let me know. Thank you in advance for your assistance.

<root>Statics
-->sun.misc.SoftCache->java.util.HashMap->java.util.Has
Map$Entry[]->java.util.HashMap$Entry->java.net.URL
I do not an instance of HashMap in my class.
Therefore, the HashMap is either created by URLclass
or the
com.symantec.itools.javax.swing.icons.ImageIcon
class.SoftCache seems to have a normal HashMap inside
it/* Hash table mapping keys to ValueCells */
private Map hash;but if that is the HashMap in JProbe
information then the URL would have to be a key in
the map - otherwise there'd be another object in the
chain of class SoftCache.ValueCell
are you certain that the java.net.URL's in that
hashmap are your ones?
out of curiosity - are you certain that the URL's are
the/a problem (are you getting an OutOfMemoryError?)
asjfThe button that contains the URL's is the only one on the JInternalFrame. The JProbe Memory Debugger displays the java.net package name, the URL class name, the count (2), and the Count Change (+2). When I remove the button from the JInternalFrame, the aforementioned numbers on the Instance Summary remain the same. The snapshot of the Java Heap reveals that the two instances of the URL class are still there. The Memory Leak Doctor shows the reference graph from the root set:
<root>Statics->SoftCache->HashMap->HashMap$Entry[]->HashMap$Entry->URL
When I right click on the arrow between HashMap$Entry[] and HashMap$Entry to remove the reference, I receive the message: "Congratulations this object can be garbage collected..." It appears like private instance of Map in SoftCache is holding a strong reference.
I am not getting an OutOfMemoryError exception.

Local ref garbage collection within "nested" JNI calls

I am using a JVM started in C++ to make calls to java classes. The C++ code makes JNI call into the JVM which instantiates a java class. The java class, in the course of execution, makes other JNI calls. All this happens on one thread of execution.
What I am seeing is that local references from the native methods being called by the java class are not being released until the initial C++ native call exits. The JNI spec (text included below) seems to indicate there is registry of "nonmovable local references to Java objects" which "keeps the objects from being garbage collected". Is there only one such registry which does not get deleted until the initial C++ native call exits? If so, this would explain what I am seeing. How do I get around it?
Thanks,
Iztok
From the JNI spec:
"To implement local references, the Java VM creates a registry for each
transition of control from Java to a native method. A registry maps nonmovable local references to Java objects, and keeps the objects from being garbage collected. All Java objects passed to the native method (including those that are returned as the results of JNI function calls) are automatically added to the registry. The registry is deleted after the native method returns, allowing all of its entries to be garbage collected."

When I say "initial" I mean the initial C++ JNI call into a JVM running in a C++ process as shown in the pseudo code below. initNativeFunc() makes a call to Foo.doSomething() function which calls nativeFunc2 (another native function). Only a local reference to Retval was created in nativeFunct2, so when nativeFunct2 returns and the Retval is no longer used in Foo it should be a candidate for garbage collection. But this is not what happens. The Retval from nativeFunc2 is not being cleaned up until Foo.doSomething() returns. If I make the loop in Foo.doSomething() long enough, NewDoubleArray() returns a NULL when it runs out of memory.
void initNativeFunc() {
jclass clazz = env->FindClass("Foo");
jmethodID mid = env->GetMethodID(clazz, "doSomething", "()V");
env->CallVoidMethod(clazz, mid, ...);
JNIEXPORT jobject JNICALL nativeFunc2() {
jclass clazz = env->FindClass("Retval");
jmethodID mid = env->GetMethodID("Retval, "<init>", "()V");
jobject retval= env->NewObject(clazz, mid);
jdoubleArray da = env->NewDoubleArray(100000);
jfieldID fid = ...
env->SetObjectField(retval, fid, da);
return retval;
public class Foo {
public native void nativeFunc2();
public void doSomething() {
for (int i = 0; i < 100; i++) {
Retval retval = nativeFunc2();
}

A question about JNI references, persistence, and garbage collection

I am writing a library to allow our Java developers to access C functions in our product. I want people on the Java side to be able to instantiate instances of a new object (on the C side), say "Map", and I want those objects to persist until they are destroyed on the Java side. I am thinking of creating a wrapper for the native methods, which stores an identifier for the instance of an object. When the C object is accessed, the identifier is passed to the C code which looks up the correct object in a table. I understand that if I use the NewGlobalReference call in JNI I can get objects to persist.
When it is time for garbage collection I plan to override finalize() to call the C code and tell it to remove the Global Reference.
Here's what I have in mind
public class JMap() {
     private static int id;
     static {
          System.loadLibrary("libMap");
          /*Call C method which instantiates object and creates a GlobalReference
          which is stored in table. Returns ID for reference*/
          id = _init();
     public void setSize(int x, int y) {
          _setSize(id, x, y);
     public void finalize() {
          _finalize(id);
          super.finalize();
     private native int _init();
     /*calls DeleteGlobalReference for the reference matching this id*/
     private native void _finalize(int id);
     private native void _setSize(int id, int x, int y);
}Is this the right thing to do? Have I understood the way JNI works with regard to GlobalReferences?
Any comments, tips or pointers would be appreciated :)

This probably should have been posted in the Native Methods sub-forum, I have reposted there:
http://forum.java.sun.com/thread.jspa?threadID=657667
Mods please delete this post :)

BufferedWriter I/O Garbage Collection!?

Ack! I cannot come up with an I/O solution that doesn't produce a lot of objects for collection. I'm sure there has to be a way, but at this point I'm at a loss. I recently noticed after downloading Optimizeit and watching object creation, that everytime I write to an output stream (in my case it's BufferedWriter going out to a socket), it creates new byte[] objects in large quantities, which are then available for garbage collection. This normally wouldn't be an issue, but if I wrap my code around a for loop that outputs a lot of data, I've generated quite a lot of instances. (I have a memory leak somewhere in my code, looking at object creation is about all I can do to find it)
For example, assume I have a StringBuffer _Buffmessage.
I also have a character array out_message.
os is my outputStream.
os = new BufferedWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
//loop through StringBuffer and copy into a character array to prevent creation of String object
//(alternative to using toString() method of StringBuffer
for(int i = 0 ; i < _Bufmessage.length(); i ++)
out_message[i] = _Bufmessage.charAt(i);
//write out character array to client
os.write(out_message, 0, _Bufmessage.length());
os.newLine();
os.flush();If I run this code around 2000 times, I end up generating thousands of instances of byte[] ready for collection after running os.flush(); There HAS to be a way around this, or should I even be concerned about this? Am I somehow creating an object for each byte in the stream?

Here's a follow up and the solution I found. The two suggestions I recieved were:
Suggestion 1:
StringBuffer input;
OutputStream out;
out.write( input.toString().getBytes());
out.close();and Suggestion 2:
StringBuffer input;
OutputStream out;
byte[] outArray = input.toString().getBytes();
out.write(outArray,0,outArray.length );
out.close();However a combination of my original solution as well as the suggested solutions resulted in the fix. In Suggestion 1, every call to write would create an instance of string (bad) and then write the byte array. In Suggestion 2, every call would result in the creation of a string (bad), creation of a byte array(bad), and a dupe of that array into write (ick). This was really an issue since I was outputting around 3-4 thousand times. My final solution is as follows; creates no new instances and is able to write out to my outputstream:
byte[] outArray = new byte[2000]; //byte array for output
OutputStream os = clientSocket.getOutputStream(); //this is the socket outputstream to write to
//for loop here, processing data......
try
//fill the byte array with chars from StringBuffer - reuse the existing array to
//avoid multiple instances being created
for(count = 0 ; count < _Bufmessage.length(); count ++)
   outArray[count] = (byte)_Bufmessage.charAt(count);
//cast a new line byte to the output
outArray[count] = (byte)'\n';
//write out the length of the string
os.write(outArray,0,_Bufmessage.length());
}viola my memory leak was plugged - data is written to output, no char[] or byte[], nor String instances are generated, and I can sleep! As a sidenote, I did end up converting to NIO, and the new I/O classes eliminate these problems. I thought I'd share the solution anyway. Thanks to you three who gave me suggestions and didn't give me a hard time being a first time poster ;)

At which line , Object is Garbage collected.

1. public class GC {
2. private Object o;
3.   private void doSomethingElse(Object obj) { o = obj; }
4.   public void doSomething() {
5. Object o = new Object();
6. doSomethingElse(o);
7.   o = new Object();
8.   doSomethingElse(null);
9 o = null; 10. }
} When the doSomething method is called, after which line does the Object created in line 5 become available for garbage collection?
A. Line 5
B. Line 6
C. Line 7
D. Line 8
E. Line 9
F. Line 10
I think it should be line 9.but answer is 8....
How is it line 8?
Edited by: user12203354 on Nov 4, 2012 9:38 PM

You've already ask a similar question in your other thread where I ask you to answer some questions.
Question on Garbage collection
You may want to work on one question like this at a time until you understand the difference between an object and a variable that references an object.

API for Garbage Collection

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